The present invention relates to a bromination of the side chain of m-phenoxytoluene by using a polyhaloethane as a brominating agent.
m-Phenoxybenzylbromide and m-phenoxybenzylidenedibromide obtained by a bromination of the side chain of m-phenoxytoluene are important intermediates for syntheses of synthetic pyrethroid type insecticides which have been recently found.
It has been reported that a bromination of the phenyl nucleus is resulted together with the bromination of the side chain of m-phenoxytoluene by using bromine as the brominating agent in the bromination of the side chain of m-phenoxytoluene.
The by-product of a phenyl nucleus brominated substituent causes a lower yield and trouble in industrial production because of the difficulty of a separation from the object side chain brominated product.
In order to decrease a production of the phenyl nucleus brominated substituent, it has been proposed to carry out the bromination of the side chain of m-phenoxytoluene with bromine at higher than 220.degree. C. in the presence of phosphorus halides as disclosed in U.S. Pat. No. 4,014,940 and to carry out the bromination at higher than 180.degree. C. under irradiation of ultraviolet rays as disclosed in U.S. Pat. No. 4,010,087. These processes are effective for decreasing the production of the by-product of the phenyl nucleus brominated substituent, but are not satisfactory since several % of the by-product is produced.